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From: Nikanth Karthikesan <knikanth@suse.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	xfs-masters@oss.sgi.com, xfs@oss.sgi.com,
	Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [xfs-masters] [RESEND][PATCH 6/7] xfs: Remove code handling bio_alloc failure with __GFP_WAIT
Date: Mon, 20 Apr 2009 13:53:35 +0530	[thread overview]
Message-ID: <200904201353.35858.knikanth@suse.de> (raw)
In-Reply-To: <20090420010237.GF16929@discord.disaster>

On Monday 20 April 2009 06:32:37 Dave Chinner wrote:
> On Wed, Apr 15, 2009 at 04:09:30PM +0530, Nikanth Karthikesan wrote:
> > Resending as I accidentally missed Jens earlier.
> >
> > Jens, can you merge this as well.
> >
> > Thanks
> > Nikanth
> >
> > Remove code handling bio_alloc failure with __GFP_WAIT.
> > GFP_NOIO implies __GFP_WAIT.
>
> Not sure that is right. The intent of the code is that if we can't
> get a large bio immediately, try a smaller one which is more likely
> to succeed when we are under memory pressure. i.e. we will get IO
> moving faster than if we waited for a maximally sized biovec to be
> allocated.
>
> IOWs, I don't think __GFP_WAIT is implied by this code, regardless
> of what GFP_NOIO actually means now. The same code fragment can be
> found in NILFS, and it uses GFP_NOWAIT, not GFP_NOIO. I suspect that
> this is what this XFS code should be changed to use to retain the
> original intent of the code....
>

Yes, if that is the intent, it needs to be changed as GFP_NOWAIT. Otherwise 
the first attempt to get a larger bio itself would return only after it 
succeeds, which makes the logic useless.

Thanks
Nikanth

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  reply	other threads:[~2009-04-20  8:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-15 10:39 [RESEND][PATCH 6/7] xfs: Remove code handling bio_alloc failure with __GFP_WAIT Nikanth Karthikesan
2009-04-20  1:02 ` [xfs-masters] " Dave Chinner
2009-04-20  8:23   ` Nikanth Karthikesan [this message]
2009-04-22  6:45   ` [PATCH] xfs: fix xfs_alloc_ioend_bio code to try and get atleast a smaller bio Nikanth Karthikesan

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